Measuring an electrical voltage on a metal-encapsulated switchgear

Abstract

A measuring apparatus for measuring an electrical voltage for a metal-encapsulated switchgear. The measuring apparatus has an electrical conductor, an electrically conductive measuring electrode, which surrounds a first conductor portion of the electrical conductor and is electrically insulated from the electrical conductor, and an electrically conductive field control electrode, which is electrically insulated from the electrical conductor and from the measuring electrode and which has a first field control electrode portion that surrounds the measuring electrode.

The invention claimed is: 
     
       1. A measuring apparatus for measuring an electrical voltage for a metal-encapsulated switchgear, the measuring apparatus comprising:
 an electrical conductor; 
 an electrically conductive measuring electrode that surrounds a conductor portion of the electrical conductor and is electrically insulated from said electrical conductor; and 
 an electrically conductive field control electrode that is electrically insulated from said electrical conductor and from said measuring electrode; 
 said field control electrode having a field control electrode portion that surrounds said measuring electrode; 
 wherein said conductor portion of said electrical conductor is a first conductor portion and said field control electrode portion of said field control electrode that surrounds said measuring electrode is a first field control electrode portion; 
 said field control electrode further comprising a second field control electrode portion that surrounds a second conductor portion of said electrical conductor; and 
 said second field control electrode portion having a maximum diameter in a plane perpendicular to said electrical conductor that is smaller than a diameter of said first field control electrode portion. 
 
     
     
       2. The measuring apparatus according to  claim 1 , wherein said measuring electrode has a U-shaped profile with two legs that face away from said electrical conductor. 
     
     
       3. The measuring apparatus according to  claim 1 , wherein said field control electrode is formed of field control electrode segments that are arranged one after another along a path extending around said electrical conductor. 
     
     
       4. The measuring apparatus according to  claim 1 , wherein said measuring electrode is formed of measuring electrode segments that are arranged one after another along a path extending around said electrical conductor. 
     
     
       5. The measuring apparatus according to  claim 1 , further comprising a measuring coil for current measurement surrounded by said field control electrode and extending around said electrical conductor, wherein said measuring coil is electrically insulated from said field control electrode, from said electrical conductor, and from said measuring electrode. 
     
     
       6. The measuring apparatus according to  claim 5 , wherein said measuring coil is a Rogowski coil. 
     
     
       7. The measuring apparatus according to  claim 5 , wherein said measuring coil is arranged between said measuring electrode and said field control electrode. 
     
     
       8. The measuring apparatus according to  claim 5 , wherein said measuring electrode and said measuring coil are arranged one after another along said electrical conductor. 
     
     
       9. A method of measuring an electrical voltage, the method comprising:
 providing a measuring apparatus configured for measuring the electrical voltage at an electrical conductor with respect to a reference potential; 
 the measuring apparatus comprising:
 the electrical conductor; 
 an electrically conductive measuring electrode that surrounds a conductor portion of the electrical conductor and is electrically insulated from said electrical conductor; and 
 an electrically conductive field control electrode that is electrically insulated from said electrical conductor and from said measuring electrode; 
 said field control electrode having a field control electrode portion that surrounds said measuring electrode; 
 
 measuring a measurement voltage that is present at the measuring electrode of the measuring apparatus with respect to the reference potential; and 
 ascertaining the voltage present at the electrical conductor of the measuring apparatus with respect to the reference potential from the measurement voltage. 
 
     
     
       10. A metal-encapsulated switchgear for selectively interrupting and closing an electrical current path, comprising:
 a measuring apparatus according to  claim 1 ; 
 wherein the electrical current path passes through the electrical conductor of said measuring apparatus. 
 
     
     
       11. The switchgear according to  claim 10 , wherein the field control electrode of the measuring apparatus is at a ground potential. 
     
     
       12. The switchgear according to  claim 10 , further comprising a metal housing and a bushing in said housing, wherein the electrical conductor of the measuring apparatus extends through said bushing and the field control electrode is arranged in said bushing. 
     
     
       13. The switchgear according to  claim 10  being a power switch or a circuit breaker.